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18F-FDG PET/CT is a useful modality for identifying high-glucose-consuming cells, such as cancer cells by the glucose metabolism of FDG. FDG is taken up by cancer and inflammatory cells but occasionally, there is some FDG uptake on normal tissues as a result of their individual physiological characteristics. In particular, in fertile females, unusual FDG uptake in the breast changes according to the stages in the menstrual cycle, which can adversely affect a diagnosis. Therefore, this study examined the change in breast FDG uptake in the menstrual cycle on 18F-FDG PET/CT. One hundred and sixty females (34 ± 3.5 years old), who had not undergone a gynecologic anamnesis and had a regular menstrual cycle over the previous 6 months, were examined from March 2011 to February 2012. The subjects were divided into the following 4 groups (each with 40 patients): flow phase, proliferative phase, ovulatory phase and secretory phase using Pregnancy Calculator 0.14 and history taking. Discovery STE (GE Healthcare, USA) was used as the PET/CT. The SUVs on the accumulated region on the breast were analyzed, and 3 nuclear medicine specialists performed a blind test. The SUVs on the breast were the flow phase (1.64 ± 0.25), proliferative phase (0.93 ± 0.28), ovulatory phase (1.66 ± 0.26) and secretory phase (1.77 ± 0.28). Higher uptake values were observed in the secretory, flow phase and ovulatory phase (p< 0.05). The accumulation of the breast was divided into the following 3 grades compared to the lung and liver by gross analysis: the breast uptake was equal to the lung (Grade I); between the lung and liver (Grade II); and equal to or greater than the liver (Grade III). These results showed a high uptake value in the secretory, flow phase and ovulatory phase (p <0.05). In fertile females, the FDG uptake of the breast showed changes according to the menstrual cycle, which can be used to improve the diagnosis of breast disease. Therefore, the false-negative findings of breast disease can be reduced by performing an examination at the appropriate period through history taking and considering the individual menstrual cycle.

PET/CT system reduces the scanning time and provides an anatomical image because it realizes a CT-based attenuation corrected image without using an isotope, such as 68 Ge or 137Cs, in the attenuation correcting method due to the recent technological development. On the other hand, artifacts are generated in a CT image by dental materials, which affect the attenuation corrected PET image. Against this backdrop, this study performed a clinical experiment and a phantom experiment. The clinical experiment targeted 40 patients without oral disease, including 20 patients who had metal prosthesis in their tooth and 20 patients who had a dental implant in tooth. In the phantom experiment, a dental cast was used for a PET/CT scan after the metal prosthesis and the dental implant was inserted in the original dental phantom to make a dental cast. According to the study results, when the patients had metal prosthesis, standard uptake value (SUV) decreased by approximately 19.6% in the dark streak artifact region and increased by approximately 90.1% in the bright streak artifact region, compared with the artifact free region. In the phantom with metal prosthesis, the SUV decreased by approximately 18.1% in the dark streak artifact region and increased by 18.0% in the bright streak artifact region, compared to the artifact free region. When the patients with dental implant, the SUV decreased by approximately 19.1% in the dark streak artifact region and increased by 96.6% in the bright streak artifact region, compared with the artifact free region. In the phantom with dental implant, the SUV decreased by approximately 14.4% in the dark streak artifact region and increased by 7.0% in the bright streak artifact region, compared to the artifact free region. Therefore, by considering these results, we can improve the diagnostic accuracy in oral and maxillofacial cancer.

The number of PET/CT tests for diagnosing and treating tumors are increasing every year, and thus it is considered necessary to compare PET/CT images among medical institutions or among different PET/CT systems within the same medical institution. We present to get the variation of standardized uptake values (SUV) among PET/CT systems, to derive an SUV calibration table that enables quantitative comparison of PET/CT systems, and to test the usefulness of the calibration table through comparing patient's SUV with the SUV calibration table. The correlation coefficients that inter-compared the calibration constants of normal patients and the calibration constants of the mean standardized uptake value with the calibration constants of the standardized uptake value of phantom are 0.88938 (P<0.0001)., (Copyright © 2010 Elsevier Ltd. All rights reserved.)